The following correction was printed in the Guardian's Corrections and clarifications column, Thursday 28 January 2010

The report below described Tony Blair as UN envoy in the Middle East. Mr Blair acts as a special envoy on behalf of the "Quartet", comprising the UN, the United States, Russia and the European Union.

Tony Blair will add to the riches he has made since leaving office after agreeing to become a paid speaker for Lansdowne Partners, a London-based hedge fund managed by a major Tory party donor.

Blair will give some private speeches to staff of the Mayfair-based fund this year, potentially earning him hundreds of thousands of pounds, it has emerged.

The former prime minister's spokesman declined to comment on his fees, although he is reported to earn as much as £180,000 for 90 minutes for his thoughts on geopolitical matters in countries from Spain to the Philippines. That works out at about £2,000 a minute.

"He [Blair] remains one of the most popular speakers around the world," the spokesman said.

Blair, 56, has made more than £10m since leaving office from deals including books, advisory roles and event appearances. He is reported to have received £4.6m for his memoirs, to be published by Random House after the general election. Blair also receives about £2m for an advisory and representative role with US investment bank JP Morgan, and another half a million from Zurich Financial Services. He has a £63,000 annual pension, funded by UK taxpayers.

However, he spends most of his time as the UN envoy in the Middle East, a job that is unpaid, the spokesman said. Blair spends between one week and 10 days a month in the region, away from his £4m Connaught Square home in central London.

But talking to a hedge fund is likely to spark anger in the Labour party as it tries to toughen regulation and impose heavier taxes on the financial sector.

Lansdowne became known for making money by betting on the fall of Barclays and Northern Rock shares at the peak of the credit crunch. The fund made an estimated £100m from the demise of the now nationalised Northern Rock.

The move is also controversial because one of the firm's founders, the former Goldman Sachs banker Paul Ruddock, has donated about £260,000 to the Conservative party. The sum is enough to secure him membership of the Tory leader's 100-strong elite donors' club without denting his estimated £350m personal fortune. After his firm sold a 20% stake to Morgan Stanley, Ruddock now carries out some philanthropic jobs, including being the chairman of the board of trustees of the Victoria & Albert museum.

Blair follows the steps of two former Conservative leaders into the lucrative hedge fund sector. The London-based Centaurus fund used to employ Kenneth Clarke, the shadow business secretary, and the former Spanish prime minister José María Aznar until they were removed from the board after losses by the fund linked to the credit crunch.

Hedge funds often employ former politicians to gain better knowledge of the political and investment climate in certain countries or sectors. Their knowledge of how governments work and their network of contacts help financiers gain information before deciding on an investment.

In this case, Blair will not talk to Lansdowne clients but only to some of the firm's 100 global staff. Blair, who still defends his decision to invade Iraq in his speeches, arranges his talks and appearances through the Washington Speakers Bureau, an agency for public figures such as Sarah Palin and George Bush.